Apparatus and method for repairing failure spots on subterranean well tubulars using shock waves

Abstract

An apparatus and method are disclosed for the repair of failure spots, such as holes, crevices, and the like, along a first tubular section, such as casing section(s) in subterranean wells. The apparatus includes a housing made of a malleable material, such as steel, which is responsive to shock waves generated by an explosive material, such as a detonator cord, carried inside the housing. The explosive detonator cord is activated to generate shock waves within the housing to expand the malleable housing to conform to the wall holes, openings and failure spots in the casing. Thereafter, a head, selectively securable to the housing, is disengaged from the housing during retrieval of the head after activation of the detonator cord, to retrieve the head from the well and leave the malleable housing intact and across the failure spots.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus and method for the repair of failure spots along a first tubular conduit, such as casing, in a subterranean well.

2. Brief Description of the Prior Art

Subterranean wells, such as oil, gas or water wells, oftentimes are completed with the introduction and cementing in place a long string of tubular sections of metallic casing. Since the expected production life of such a well has been known to last decades, and in view of the fact that the abrasive well fluids and treatment chemicals flowing interiorally of the casing often result in defects, such as small holes, pock marks leading to small holes and cracks, (“failure spots”) it is not at all surprising that a failure in circulation of the fluids oftentimes results, with the holes eventually getting larger and larger and even penetrating through the cement securing the casing within the well. It is therefore necessary from time to time to inspect the casing for such defects and attempt to repair them, as opposed to retrieving the entire casing string and running and setting another string of casing, or running a smaller diameter casing string which greatly reduces the diameter available for production.

U.S. Pat. No. 6,536,349, entitled “Explosive System For Casing Damage Repair”, to Patterson, et. al., discloses use of a liquid explosive to repair a damaged portion of casing where the damaged portion restricts access through the casing string. However, this concept does not address the problem of actual repair of failure spots, such that the original casing section is returned to normal or substantially normal specifications for subsequent production or other actions.

SUMMARY OF THE INVENTION

The invention related to an apparatus and method for the repair of failure spots in and along a first tubular conduit, such as casing, placed within a subterranean well. The apparatus includes a malleable cylindrical housing mean which is responsive to shock waves generated within the interior of the housing to outwardly and radially expand the housing across the and into the failure spots. Means, such as a detonator cord, are provided within the housing to generate the shock waves upon explosive activation for expansion of the housing means. Actuation means, such as an electric activator, are also provided for activating the detonator cord, or the like. In one embodiment, a head element is provided which has means for securing the head element to one end of the housing. The head element is selectively disengageable from the housing after activation of the detonator cord or charge, such the housing remains in place over the repaired failure spots and the head is retrieved by wire line or conduit, out of the well.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of a section of first tubular conduit, or casing, cemented within a subterranean well, and containing failure spots that are required to be repaired.

FIG. 2 is a view similar to that of FIG. 1, illustrating the positioning of the apparatus of the present invention on a wire line or other conduit and positioned to straddle the failure sport on the casing conduit.

FIG. 3, is an illustration similar to that of FIG. 2, illustrating the apparatus during activation and explosion of the detonator cord to generate shock waves to expand the housing into and over the failure sport in the casing.

FIG. 4, illustrates the housing covering the failure spots, with the head element shearingly disengaged from the housing and retrieved from within the well.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring to FIG. 1, there is shown a subterranean well W. The well W includes previously run and set a first conduit string or casing C-1. As shown, the casing C-1 has a series of small holes or defects H located longitudinally and radially around a section of the casing C-1. These “failure spots” are required to be repaired.

As shown in FIG. 2, the apparatus 100 is shown positioned within the well W and straddeling the failure spots H. The tool 100 is run into the well on an electric line, tubing, or wire cable, or the like, illustrated as 102. The tool 100 is comprised of two major parts: an upper head element 103, to which is secured the cable 102; and a cylindrical housing 105, made of a malleable material, such as iron, thin sheet metal alloys, tin or the like. The housing 105 may be made of any similar malleable material which will permit radial expansion in response to shock waves generated by an explosive charge within the housing 105. The head element is secured to the uppermost portion of the housing 105 by means of shear pins 104. The pins 104 will separate when a predetermined amount of shear or pulling gforce is applied through the pins 104 as the head element 103 is retrieved from the well W subsequent to the repair of the failure spots, as hereinafter described.

An electric line 101 is carried through the head element 103 and into the housing 105 for securement to a detonator cord or charge 106. As used herein a detonator or detonating cord is a round, flexible cord containing a center core of high explosive. It is relatively insensitive and requires a proper detonator, such as a No. 6 strength cap, for initiation. Detonating is used to initiate other explosives, its ability to detonate the other depends in part on the density of the high explosive core (usually pentaerythritol tetranitrate: PETN) or the grains of PETN per linear foot of cord. The most widely used cords have approximately 25 to 60 grains-per foot (5.3 to 12.87) grams per meter), although core load with as little as four grains per foot and up to 400 grains per foot is available.

As further used herein, the term “detonating cord” or “detonator” has its usual meaning of flexible, coilable cord having a core of high explosive, the core being a secondary explosive, usually PETN. The term “low energy detonating cord” or “LEDC”, is conventionally used to mean detonating cord which will not reliably initiate itself when placed in contact with itself by coiling or crossing lengths of the cord, and which will not, when in an ungathered configuration, reliably directly initiate a less sensitive or secondary explosive receptor charge, e.g., those that comprise secondary explosive materials (e.g., Pentolite mixtures of PETN and trinitrotoluene (“TNT”) to the substantial exclusion of primary explosive materials. Such ungathered configurations include, e.g., simple surface-to-surface contact between an uncoiled LEDC and a receptor charge and the insertion of the end of a substantially straight length of LEDC into a bore in the body of a receptor charge. For This reason, LEDC is typically used to initiate a more sensitive, high energy amplifying device such as a detonator which is sensitive to the LEDC (usually by virtue of containing a primary explosive material) and which generates an output signal sufficient to initiate the less sensitive secondary explosive receptor charge.

Now referring to FIG. 3, after the tool 100 is located within the well W to straddle the failure spots H in the casing C-1, the detonator cord 106 is exploded by sending an electric signal through electric line 101 from the top of the well W or other location within the well W. As the detonator cord 106 is activated, an explosion occurs to direct shock waves radially outwardly and against the housing 105. Because of the malleable nature of the construction of the housing 105, the shock waves S will cause it to expand outwardly, filling and otherwise repairing the failure spots H. Thereafter, the head element 103 is released from the housing 105 as the line or tubing 102 is pulled upwardly, such the shear pins 104 shear. The housing 105 is thus left in the well W.

Although the invention has been described in terms of specified embodiments which are set forth in detail, it should be understood that this is by illustration only that the invention is not necessarily limited thereto, since alternative embodiments and operating techniques will become apparent to those skilled in the art in view of the disclosure. Accordingly, modifications are contemplated which can be made without departing from the spirit of the described invention.

Claims

1) An apparatus for introduction into a subterranean well on a conduit for the repair of failure spots along a first tubular section encased within said well, comprising:

(a) a malleable cylindrical housing means responsive to shock waves generated within said housing to outwardly and radially expand said housing across and into said failure spots;

(b) means within said housing to generate shock waves to initiate expansion of said housing; and

(c) actuation means for actuating said means to generate said shock waves.

2) The apparatus of claim 1, further comprising: a head element initially secured to one end of said housing and selectively disengagable there from subsequent to expansion of said housing, said head element having means for securing said conduit thereto for introduction, setting and retrieval of said head element within the well, whereby the expanded housing is retained within said well and the head is retrieved from within the well.

3) The apparatus of claim 1 wherein the means within said housing to generate shock waves comprises an elongated section of detonator cord.

4) A method for the repair of failure spots within or along a first tubular section encased within said well, comprising the steps of:

(1) introducing into the well on a conduit an apparatus, comprising: (a) a malleable cylindrical housing means responsive to shock waves generated within said housing to outwardly and radially expand said housing across and into said failure spots; (b) means within said housing to generate shock waves to initiate expansion of said housing; and (c) actuation means for actuating said means to generate said shock waves;

(2) positioning the apparatus in the well whereby the cylindrical housing means straddles the failure spots; and

(2) actuating the actuation means to cause said means within said housing to generate shock waves to initiate expansion of said housing, whereby said housing is expanded into and across said failure spots.

5) The method of claim 4 wherein said apparatus further comprises a head element initially secured to one end of said housing and is selectively disengageable there from, and means for securement of said head element for introduction, setting and retrieval of said head element within the well; and further comprising the step of releasing the head element from the housing subsequent to generation of said shock waves and retrieving the head means from within the well.